What are the clinical presentation and management of a patient with suspected herniation syndrome, particularly one with a history of stroke, tumor, or traumatic brain injury?

Herniation Syndrome: Classic Triad and Clinical Recognition

The classic triad of herniation syndrome consists of: (1) altered level of consciousness/coma, (2) ipsilateral pupillary dilation (mydriasis), and (3) contralateral hemiparesis. 1, 2, 3

Clinical Presentation

Core Features of the Triad

• Altered consciousness: Progressive decline in Glasgow Coma Scale (GCS) score, typically GCS ≤8, representing compression of the reticular activating system 1, 2
• Pupillary abnormalities: Ipsilateral pupil dilation (anisocoria) due to compression of the third cranial nerve as the uncus herniates over the tentorial edge 1, 2, 3
• Motor deficits: Contralateral hemiparesis or hemiplegia from compression of the cerebral peduncle, though paradoxically can be ipsilateral (Kernohan's notch phenomenon) 3

Additional Warning Signs

• Cushing's triad (late finding): Hypertension, bradycardia, and irregular respirations indicating imminent brainstem compression 3
• Bilateral pupil dilation: Indicates advanced herniation with extremely poor prognosis 2
• Posturing: Decorticate or decerebrate posturing reflects severe brainstem dysfunction 3

Critical caveat: Rare cases of "sliding uncus syndrome" can present with herniation on imaging while the patient remains fully conscious, though this is exceptional 4

Immediate Management Algorithm

Step 1: Airway and Oxygenation (First 5 Minutes)

• Intubate immediately if GCS ≤8 or rapidly deteriorating consciousness 1
• Target PaO2 ≥13 kPa (approximately 98 mmHg) while avoiding hyperoxia 5, 1
• Position head-up 20-30 degrees to facilitate venous drainage 5
• Apply minimum 5 cmH2O PEEP to prevent atelectasis (up to 10 cmH2O does not worsen cerebral perfusion) 5

Step 2: Osmotherapy (Within 15 Minutes)

Administer one of the following immediately 5, 1:

• Mannitol 20% at 0.5 g/kg IV bolus over 15-20 minutes 5, 1
• OR hypertonic saline 3% at 2 ml/kg IV bolus 5, 1
• Equiosmotic dosing: Approximately 250 mOsm for either agent 5

Critical safety threshold: Monitor serum osmolality and never exceed 320 mOsm/L to prevent renal failure, seizures, hemorrhagic encephalopathy, and osmotic demyelination syndrome 6

Step 3: Ventilation Strategy

• Maintain PaCO2 35-40 mmHg under normal circumstances 5
• Short-term hyperventilation (PaCO2 4.0-4.5 kPa or approximately 30-34 mmHg) is justified only for impending herniation, as prolonged hypocapnia worsens cerebral ischemia 5, 1
• Never use prophylactic hyperventilation as it exacerbates secondary ischemic injury 5, 1

Step 4: Blood Pressure Management

For traumatic brain injury with herniation 5, 1:

• Maintain systolic BP >110 mmHg (ideally >100 mmHg minimum)
• Maintain MAP >90 mmHg (or >80 mmHg minimum)
• Measure arterial pressure at the level of the tragus when head is elevated 5

For stroke/tumor with herniation 5, 7:

• Avoid aggressive BP lowering as elevated BP may be compensatory to maintain cerebral perfusion pressure against elevated ICP 5
• Correct hypovolemia first with 0.9% saline before using vasopressors 5, 7

Step 5: Fluid Management

• Use only 0.9% saline as it is the only commonly available isotonic crystalloid appropriate for brain injury 5, 1
• Avoid hypotonic fluids: Ringer's lactate, Ringer's acetate, and all colloids (including gelatins and 4% albumin) worsen cerebral edema 5, 1
• Reverse hypovolemia aggressively as hypotension adversely affects neurological outcome 5

Step 6: Coagulation Correction (If Applicable)

For patients requiring emergency neurosurgery 5:

• Platelet count >50,000/mm³ (higher values advisable for neurosurgery) 5
• PT/aPTT <1.5 times normal control 5
• Use point-of-care testing (TEG/ROTEM) if available 5

Step 7: Definitive Neurosurgical Intervention

Obtain immediate neurosurgical consultation as herniation is uniformly fatal without intervention 1, 2

Surgical decision-making 2:

• Decompressive craniectomy indicated for: subdural hematoma, surgery timing >1 hour from herniation, and intraoperative brain swelling 2
• Craniotomy alone may suffice for epidural hematoma with minimal brain swelling and rapid intervention 2
• Surgery within 1 hour of herniation significantly improves outcomes 2

Step 8: ICP Monitoring (Post-Stabilization)

• Target CPP ≥60 mmHg when ICP monitoring available, individualized based on autoregulation status 5
• Use stepwise escalation for refractory intracranial hypertension, reserving aggressive interventions (barbiturate coma, hypothermia) for non-responders 5

Critical Pitfalls to Avoid

• Never delay neurosurgical consultation: Medical management is temporizing only; herniation requires definitive surgical decompression 1, 2
• Never allow even brief hypotension or hypoxia: Both dramatically worsen outcomes 5, 1
• Never use prolonged hyperventilation: Reserve for acute crisis only, as it causes cerebral ischemia 5, 1
• Never exceed osmolality 320 mOsm/L: Risk of catastrophic complications including osmotic demyelination 6
• Never use hypotonic fluids or albumin: These worsen cerebral edema 5, 1
• Never assume hypotension is acceptable: In trauma with brain injury, permissive hypotension is contraindicated 5, 7

Prognostic Indicators

Poor outcome predictors 2:

• Lower GCS at presentation
• Bilateral pupil dilation
• Surgery >1 hour after herniation
• Advanced age
• Subdural hematoma (versus epidural)

Overall mortality: Approximately 30% even with optimal management, with favorable outcomes in only 34% at 6 months post-injury 2